Add a fetch-cache command
Add a fetch-cache command

This command fetches from GitLab CI a cached dependency build
matching the current cerbero git commit. The cache is then relocated
and ready to be used in builds.

atsushieno/cerbero,GStreamer/cerbero,nirbheek/cerbero,GStreamer/cerbero,fluendo/cerbero,fluendo/cerbero,GStreamer/cerbero,fluendo/cerbero,atsushieno/cerbero,nirbheek/cerbero,GStreamer/cerbero,nirbheek/cerbero,fluendo/cerbero,GStreamer/cerbero,atsushieno/cerbero,atsushieno/cerbero,nirbheek/cerbero,atsushieno/cerbero,fluendo/cerbero